Drills are well known in the art and in their construction many materials have been used for the body, including the web, spiral lands, and holding shank; with cutters, or inserts, being made of a material having improved properties to provide a cutting part having a longer life.
Many steel alloys have been used for the main drill body, while carbides, for example, have been used for the cutter, or insert. Materials used for a drill body and cutters are set forth in the following patents: (1) U.S. Pat. No. Re. 19, 182; (2) U.S. Pat. No. 1,887,374; (3) U.S. Pat. No. 4,008,976; (4) U.S. Pat. No. 4,143,723; (5) U.S. Pat. No, 4,134,616; and (6) U.S. Pat. No. 4,356,873.
While inserts of a different material from the body of the drill have been used to present a harder cutting edge, none of the prior art patents discloses applicant's drill construction.